A number of well-known techniques for draining bodily fluid involve utilizing a pump, in combination with a shunt or catheter, to drain fluid from one cavity within the human body to either another cavity or to a reservoir outside of the body. Such techniques may be utilized for purposes including, for example, draining a patient's blood, urine, saliva, cerebrospinal fluid, peritoneal fluid, and/or pleural fluid, among other possibilities.
One common drainage-technique application is the drainage of pleural fluid for the treatment of pleural effusions. Pleural fluid is normally a low-protein liquid that can be found in relatively small amounts (normally a few milliliters) in a patient's pleural cavity. The pleural cavity is the space between the visceral pleura (i.e., the membrane surrounding each lung) and the parietal pleura (i.e., the membrane lining the inside of the rib cage). Pleural fluid provides a lubricating function during the breathing process and, normally, a patient's body constantly produces and absorbs pleural fluid. However, under certain abnormal conditions, such as infection, inflammation, malignancy, heart failure, liver failure, or kidney failure, among other conditions, the net flow of pleural fluid within the pleural cavity becomes unbalanced resulting in the excess accumulation (e.g., on the order of liters) of fluid in the pleural space.
Excess accumulation of pleural fluid is known as pleural effusion and may cause the pathological compression of one or both lungs—resulting in considerable difficulty or prevention of the breathing process in either or both lungs. Pleural effusion may lead to, for example, dyspnea, shortness of breath, chest pain, and/or chronic cough, greatly compromising a patient's quality of life.
Currently, pleural effusions affect approximately 1.4 million new patients each year. Over 200,000 of such pleural effusions result from malignancy and are seriously dangerous to the patients' health. More than one half of those patients with malignant pleural effusions have symptoms resulting directly from their effusion.
One treatment option for recurrent, symptomatic pleural effusions is repeated therapeutic thoracentesis. Thoracentesis involves passing a needle and catheter apparatus into the pleural cavity, at which point the needle is removed, leaving the catheter in the pleural space. The catheter remains in place and, thereby, acts as a drainage tube that leads the excess pleural fluid to a collection reservoir outside of the body. This procedure typically improves symptoms significantly. Unfortunately, malignant effusions are likely to recur and, due to patients' delays in notifying their physician that their symptoms have returned and delays in providing repeat thoracentesis, patients often spend a significant portion of their life with effusion-related symptoms. Furthermore, thoracentesis is painful and uncomfortable, and is frequently accompanied by threatening or debilitating complications, such as pneumothorax (i.e., the collapse of the lung due to accumulation of air in the pleural cavity) in up to eleven percent of patients and severe bleeding or infection in many others.
Another treatment option is chest-tube pleurodesis, which involves the obliteration of the pleural space by the instillation of a sclerosant agent via a chest tube. In this approach, a chest tube is inserted into the patient under moderate sedation or general anesthesia and the pleural fluid is drained, in a manner similar to the drainage achieved in thoracentesis. After drainage of the pleural effusion a sclerosing agent is instilled through the tube into the pleural cavity to completely coat the visceral and parietal membranes so that these membranes will permanently adhere to each other to close and eliminate the pleural cavity. Chest-tube pleurodesis can sometimes lead to long-term control of effusion-related symptoms. Unfortunately, chest-tube pleurodesis typically requires hospitalization for at least two days and as many as seven days, can be quite painful, can lead to breathing difficulties of it's own, and, in up to one third of patients, fails to provide relief of symptoms for more than a few weeks.
One variation of chest-tube pleurodesis is thoracoscopic pleurodesis, which involves the insertion of a telescope into the patient's chest by way of an intercostal incision on the patient's side. Pleural fluid is evacuated and a detailed inspection of the pleural space is undertaken so as to more discriminately apply sclerosant to regions of abnormality. In some cases, thoracoscopic pleurodesis can achieve better results than even chest-tube pleurodesis. Unfortunately, thoracoscopic pleurodesis typically requires hospitalization for four to seven days.
Yet another treatment option is chronic indwelling pleural catheters. Such indwelling catheters are placed in the patient permanently, allowing a patient to drain pleural fluid to an external reservoir on an intermittent, yet continual, basis. That is, while the pleural catheter is placed substantially inside the patient, the catheter also extends outside of the patient's body and may remain externally exposed for extended period of times. Chronic indwelling catheters have been shown to result in relatively high success rates in the management of effusion-related symptoms, and are associated with relatively short patient-hospital times of approximately one day. However, a considerable percentage of patients, approximately eight percent, fall victim to infection. Further, the patient is subject to the discomfort, irritation, and annoyance of an exposed indwelling catheter that transmits fluid to an external reservoir.
Related to indwelling pleural catheters, pleuroperitoneal shunts provide a permanent conduit between the pleural cavity and the peritoneal cavity, or the abdomen, which allows fluid to move from the pleural cavity to the peritoneal cavity, as opposed to an external reservoir. Once in the peritoneal cavity, the fluid is reabsorbed into the patients blood steam through blood and lymph vessels located in the abdomen. In popular pleuroperitoneal shunts, the shunt has a pumping chamber that must be manually activated by the patient or caregiver to move the pleural fluid. The pleuroperitoneal shunt is tunneled under the skin from the chest to the abdomen with the pumping chamber lodged in a subcutaneous pocket overlying the costal margin, or lower edge, of the rib cage. Pleuroperitoneal shunts, like chronic indwelling catheters, have been shown to result in relatively high success rates in the management of effusion-related symptoms, and are associated with relatively short patient-hospital times of approximately one day. However, also like chronic indwelling catheters, a considerable percentage of patients, approximately four percent, fall victim to infection. Further drawbacks of conventional pleuroperitoneal shunts include a relatively high rate of shunt-specific complications, such as clotting of fluid within the shunt, as well as the discomfort and inconvenience arising from manual activation of the pump by the patient.